Missed your period but not pregnant? 7 possible causes

missed period blog

No one likes getting their period. But not getting it — when you know you aren’t pregnant — can be concerning.

People assigned female at birth (AFAB) menstruate an average of 500 times in their lifetimes. The average menstrual cycle is 28 days but can range from 21 to 45 days. While every person is different, menstruation typically settles into a pattern (cycle) over time. So if that cycle gets off track, there’s usually a reason.

Reasons for a late period (that don’t include pregnancy)

If you’re not pregnant but haven’t gotten your period, you may have something called amenorrhea — the medical term for lack of a menstrual cycle. Amenorrhea is not a disease, but it is typically a symptom of another condition.

But whether you have amenorrhea or are suddenly getting your period late, it’s critical to pinpoint the cause. Having irregular menstrual cycles over time can lead to early-onset menopause.

Common reasons your period may be irregular include:

1. Age

There are two times when irregular periods are the norm: during the first several years following your first period and as you near menopause (the stopping of menstruation).

The first few years of menstruation can be a roller coaster; it’s normal for some young people to have six or more years of irregular periods. But once your body settles into a recognizable menstrual pattern, it should be smooth sailing for the next 35 or more years, perhaps interrupted only by pregnancy.

At some point — typically between the ages of 45 and 55 — your body begins the transition to menopause, which can cause missed or late periods in several ways:

  • Perimenopause: This period of transition before menopause has two stages. The early stage can cause inconsistent periods. The later stage of perimenopause can leave you waiting for your next period for more than 60 days.
  • Primary ovarian insufficiency (POI): This condition, also known as premature ovary failure, causes your estrogen levels to drop and ovaries to stop working before age 40. People with POI — about 1% of females under age 40 — have irregular or missed periods.
  • Premature or early menopause: The average age of menopause is 52. But about 5% of people AFAB experience menopause early, between age 40 and 45. If menopause occurs before age 40 and is not because of POI, it’s called premature menopause.
  • Menopause: If you’ve gone an entire year without a period, are over age 50 and don’t have amenorrhea, you may have reached menopause without realizing it.

2. Stress

Stress affects the body in many ways. It can change how you sleep, what you eat and how you function. Stress can also delay your period. Research shows that perceiving yourself as highly stressed has a direct effect on menstrual cycles in people ages 20 to 40.

If you are stressed all the time (chronic stress), your period may stop altogether. A stressed body makes more cortisol hormone, which can affect the part of your brain that regulates menstruation (hypothalamus). When periods stop because the hypothalamus isn’t functioning properly, it’s called hypothalamic amenorrhea.

3. Polycystic ovary syndrome (PCOS)

When people AFAB have high levels of male hormones (androgens), they may be diagnosed with polycystic ovary syndrome (PCOS). Because of the hormonal imbalance, cysts (abnormal pockets of fluid) often form on the ovaries and cause ovulation to stop.

If your missed or irregular periods are due to PCOS, you’ll likely have other symptoms, such as:

  • Acne on the face, chest and back
  • Darkening skin, particularly in skin folds
  • Excessive hair (hirsutism) on the face, chin or chest
  • Skin tags (painless flaps of skin) on the upper body
  • Weight gain or difficulty with weight loss

4. Weight

Weighing too much or too little can impact monthly cycles. A low body weight or an eating disorder can pause ovulation or make periods irregular. If you aren’t getting the proper nutrients — or your body can’t absorb them — you can’t produce hormones to regulate periods. If you lose weight too quickly, menstruation can completely stop.

Weighing too much can also affect your periods. A high body mass index (BMI) and obesity can cause changes in hormone levels — specifically estrogen and progesterone — which throw off menstrual cycles. Weight gain and obesity are also associated with an increased risk and worsening of PCOS.

5. Birth control

Many forms of birth control rely on hormones to affect ovulation. But the hormonal transition that happens when starting, stopping or changing birth control can wreak havoc on your menstrual cycle. In some cases, it may take three months or more to get back to regular periods.

Certain contraceptives can cause missed or lighter periods the entire time you use them. They include:

  • Birth control implants, which release hormones into your body
  • Hormonal intrauterine devices (IUDs), which reduce fertilization
  • Progestin-only pills, which may stop ovulation

If you have an IUD and aren’t getting a period at all, it’s critical to get checked out by your health care provider. There is a slight chance you could have an ectopic pregnancy — when the pregnancy implants outside the womb.

6. Thyroid issues

Your thyroid gland makes hormones to help with growth and development. But an overactive (hyperthyroidism) or underactive (hypothyroidism) thyroid can cause menstrual irregularities, including amenorrhea.

Your thyroid also regulates metabolism — the energy your body gets from food. If it’s not functioning correctly, you may experience weight loss or gain, which can also affect menstruation.

7. Chronic diseases

In addition to thyroid disorders, other chronic diseases may affect menstruation, including:

Even if a disease itself doesn’t interfere with menstruation, medication can cause issues. Medications that may cause a delay or absence of your period include:

  • Anti-epileptics
  • Anti-psychotics
  • Antidepressants
  • Chemotherapies
  • Thyroid medications

When to get help for missed or late periods

Ruling out pregnancy should be your first step after missing a period. If a pregnancy test is negative or you haven’t had sexual intercourse since your last menstrual cycle, reach out to your health care provider. They can evaluate your symptoms, look at your health history and refer you for testing if needed.

The good news is that most underlying causes of missed or late periods can be treated or reversed. Tracking your menstrual cycles and being proactive about missed or late periods can ensure you get treatment quickly.

Take the Next Step

If your periods are suddenly irregular, reach out to your primary care physician.

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